A strain sensor means a sensor which detects physical change such as tension, bending, or twisting applied to the sensor, and is applicable to various kinds of industries using characteristics of detecting such physical change. The strain sensor is available for a motion sensor which detects motion change of fingers and toes, a smart sportswear which can detect quantity of motion, shrinkage and relaxation of body joints and muscles at the time of exercise, and the like. As well as detection of human motion, it is available in various fields of manufacturing a large-area strain sensor array, a microcrack detector of device equipment, and the like through adjustment of specification and sensitivity.
As a commercialized strain sensor, there is a sensor using a metal thin film, and it is possible to detect strain by measuring resistance change generated by physical change applied to metal. Generally, a metal resistance wire with high resistivity is fixed onto an insulation substrate, a lead wire connected to a terminal is adhered to one side or both sides of a measurement object by an adhesive, and strain of the object is converted by measuring electrical resistance. Recently, there are many cases of using, instead of a resistance wire, a resistance foil as the same kind of alloy, and this is referred as a metal resistance foil strain gauge. As for the strain sensor using a metal thin film, it is difficult to embody a large area due to the nature thereof, and it is difficult to utilize the strain sensor as a sensor which detects human motion due to low sensitivity. In addition, the conventional strain sensor has a disadvantage that an error of a detection result according to a speed of strain occurrence is large.
Such a strain sensor using a metal thin film can be used only in a strain range equal to or less than about 3%, and a gauge constant (G) representing sensitivity is about 2. Meanwhile, in the human body, an elbow and a knee are strained maximally about 50%, a wrist, an ankle, or a neck is strained maximally about 20%, and a finger nodule is strained maximally about 30%. Since the conventional strain sensor using a metal thin film has a detection range of 3% or less, there is a limit to be used for a device wearing on or attached to the body.
The description as the background art is only to promote understanding of the background of the invention, and it should not be accepted as recognition of corresponding to the prior art already known to persons skilled in the art.
The description as the background art is only to promote understanding of the background of the invention, and it should not be accepted as recognition of corresponding to the prior art already known to persons skilled in the art.